Ozone is an air pollutant formed in at ground level by the chemical reaction between oxygen and automobile emissions in the presence of sunlight. The objective of this research is to determine how lung size, chemical composition, and normal functioning of the respiratory system affect the amount of inhaled ozone that reaches internal sites of tissue irritation and damage. To infer the distribution of inhaled ozone within the respiratory system, measurements of ozone concentration and air flow are made just outside the nose and mouth of healthy subjects who breathe laboratory-generated, ozonated air for about one hour. Biochemical composition of respiratory mucus is then inferred from nasal washings made with salt water. The amount of ozone that a subject retains in one of these experiments is less than the daily exposure in a large city such as New York or Los Angeles.